1. Field of the Invention
The present invention relates generally to vehicle guidance, and in particular to a system and method for global navigation satellite system (GNSS) based positioning, guidance and automatic steering allowing a user to lock onto and guide a vehicle in real time along one particular guidance path of choice, which may deviate from an initial or pre-planned guidance route, while ignoring other possible guidance paths.
2. Description of the Related Art
In the field of vehicle guidance and navigation, GNSS technology, including the Global Positioning System (GPS), has enabled a wide range of applications. For example, various GNSS receivers are available for aviation, marine and terrestrial vehicles. The GNSS information provided by such receivers can be processed and used for navigation. In more sophisticated systems, vehicle guidance can be automatically controlled using such information. For example, a predetermined travel or flight path can be programmed into an on-board computer. The vehicle guidance system can automatically maintain appropriate navigation parameters, such as course, heading, speed, altitude, etc. Control system, feedback theory and signal filtering techniques can be used to interactively anticipate (with higher order systems) and compensate for course deviations and navigation errors. Such sophisticated autopilot and automatic steering systems include computers and automated flight and steering controls integrated with manual controls.
Accurate vehicle and equipment guidance is an important objective in agriculture. For example, cultivating, tilling, planting, spraying, fertilizing, harvesting and other farming operations typically involve specialized equipment and materials, which are operated and applied by making multiple passes over cultivated fields. Ideally, the equipment is guided through accurately-spaced passes or swaths, the spacing of which is determined by the swath width of the equipment. Gaps and overlaps can occur when operators deviate from the ideal guide paths, resulting in under-coverage and over-coverage respectively. Such gaps and overlaps are detrimental to agricultural operations and can reduce crop yields. For example, gaps in coverage reduce the effective areas of fields being cultivated and treated. Overall crop production may suffer as a result. Overlaps in coverage tend to be inefficient and wasteful of materials, such as fertilizer, pesticides, herbicides, seed and fuel. Another potential problem with overlapping coverage relates to the potentially crop-damaging effects of double applications of certain agricultural chemicals.
Accurate positioning and guidance are also important in other fields, such as machine control and earth working. Controlling a vehicle's movement as well as its actual job function is important in operations such as trench digging and material hauling. Defining vehicle paths up narrow work roads in a strip mining installation, for instance, can help avoid vehicle collisions and improve safety. Guidance in almost any industrial or agricultural industry can benefit from improved guidance.
Previous mechanical systems for assisting with the guidance of agricultural equipment include foam markers, which deposit foam along the swath edges. The foam lines produced by foam markers provide operators with visible reference lines on which subsequent passes can be aligned. However, foam marking systems consume foam-making materials and provide only temporary foam marks. Moreover, guiding along such foam lines requires the operators to visually estimate the locations of the implement ends relative to the foam lines. Implements such as spray booms can span 50 feet or more, thus increasing the difficulties associated with visually aligning distant, elevated boom ends with foam lines on the ground.
Vehicles and their operators are often provided with guidance instructions from a GNSS system which receives satellite and optional local real-time kinematic (RTK) signals and translates them into a triangulated position of the vehicle in question. Depending on the GNSS system, the accuracy of a particular vehicle's position can be determined at sub-centimeter level accuracy. Systems exist that allow end users to create pre-planned guidance paths through a field or to base such a path off of a first swath within the field; however, these systems are limited to follow the paths set for them or established by a single initial row unless the user decides to manually guide the vehicle without the use of GNSS guidance for the remainder of a working period.
GNSS-based guidance is a popular and widely-used method for providing vehicle guidance today. GNSS guidance employs several different techniques to allow for optimum automated guidance of a vehicle while it is performing its job. Such guidance options include straight line A-to-B guidance, guidance based on a previous swath, or guidance based on a preplanned guide path. A more recent method for vehicle guidance utilizes a contour path or “curvature” path to guide a vehicle along complex field boundaries or in areas of widely ranging and sloping elevation. The methods of U.S. Pat. No. 7,437,230, which is incorporated herein by reference, provide a unique and useful approach to compute guidance paths based on curvature using a minimum turning radius upon which to base the allowable curve of a path.
Previous GNSS guidance systems lacking the ability to reconfigure the guidance path on-the-fly (i.e., in real-time) tended to restrict vehicle guidance to whatever pre-planned path was developed prior to the vehicle being put to work. If the vehicle operator determines that the pre-planned path is not ideal while actually working the vehicle, it is difficult to change the system to use a new guidance path. The reason for this is that many previous guidance systems, such as the Outback S3 GNSS guidance system by Hemisphere GPS LLC of Calgary, Alberta, Canada, are constantly searching for guidance points in a field or a work area. When they find a guidance point they instruct the operator or auto-steer function to follow the located guidance path. This can cause the guidance system to become confused and misguide the vehicle when one guidance path crosses another guidance path. Previously there has not been a method or system allowing a GNSS-based guidance system to ignore all but a single guidance path with the advantages and features of the present invention.